- Broken Base: The overall mood of the series is hard to read, and not everyone is pleased with the darker turn the series took after we're introduced to Musashi, and we learn about the human experiments performed on him and Jyugo. Some wanted a straight prison escape comedy, and others wish that they'd quit with the comedic bits since they're trying hard to present the serious moments as such.
- Ear Worm: Rin! Rin! Hi! Hi! is an unexpectedly catchy tune.
- Ensemble Dark Horse: The inmates of Building 5 (Liang, Upa, and Qi) are quite popular amongst fans, particularly after Season 2 gave them some well-received backstories and Character Development. The same can be said for Building 3's inmates, Trois and Honey, whose personalities were fleshed out throughout the second season.
- Ho Yay: Jyugo and Uno are very close, and it was stated that the two have known each other for a long time. Uno is shown to be caring and protective towards Jyugo, such as when he tries to stop the latter's rampage at the New Years' Tournament, then practically explodes on Hajime for nearly beating him to death. On the other hand, Jyugo finds comfort in Uno's friendship, and even states that he found a reason to look forward to the next day due to a conversation the two had.
- Jerkass Woobie: Building 5's supervisor, Samon Gokuu. He's prone to angry outbursts, particularly at Hajime, but in the second season it's revealed that his brother, Enki Gokuu, had previously killed an inmate when he was still a guard, and Samon had to deal with the aftermath of his arrest, as well as the nasty rumors and taunting from other guards who believe him to be like his brother. Then Enki escapes, brutally beats Samon, and imprisons him in the underground cells for the rest of the season.
- Moe: Most fans of the series love Nico, as his optimistic personality and Otaku hobbies endear them to him.
- Likewise, Seitarou's shy and mellow nature are endearing to many fans.
- Viewer Gender Confusion: Nico and Seitarou looked female to viewers at first glance. On the flip side, many mistook Momoko as male, probably due to her Spiky Hair and the series bursting with a Cast Full of Pretty Boys.
- The Woobie: As the series goes on, nearly every character falls into this at one point or another:
- Jyugo. The guy was born in prison, can't really function outside of it, and often gets teased for being incapable of anything except jailbreaking. It only gets worse during the New Years' Tournament, where his past of being cruelly treated as a test subject comes to light, and he's unwittingly sent on a vicious rampage, nearly killing his friends in the process. Afterwards, he's locked up in the underground cells for several days, and lives with the constant fear that Elf (one of the people who experimented on him) might come back and kill his friends if he keeps hanging around them.
YMMV / Nanbaka